Enhanced Ebook Guidelines

What is an enhanced e-book?

This term is used to describe e-books that include multimedia content, such as audio and video, or other interactive components. These books go beyond linked end notes and embedded fonts to create a more rounded reading experience; however, they do come with a few limitations. Some enhancements are not compatible with every e-book file type, and not every retailer or e-reader device supports these books. Every major retailer (iBooks, Google Play, Kindle, Kobo, and Nook) has some level of support for multimedia enhancements, although each has its own specifications for formatting and file sizes. For more info and technical specs for multimedia enhancements, see the chart at the bottom of this page.

Your editor will determine whether an enhanced e-book feature is appropriate for your project. Discuss this with your editor as early in the process as possible if this is of interest.

What enhancements can be made to an e-book?

Current technology allows for several kinds of media additions. The most basic are audio and video files, but more complicated additions such as narration are also possible. These additions are often added alongside or immediately after relevant passages in order to enhance rather than distract from the content of the text.

Audio

E-book enhancements allow audio files to be used in several ways. Audio files can be added in conjunction with relevant passages in the text and will appear in the book as icons with a play button that the reader can select when ready. Narration can also be added, allowing readers to follow along, and current words or sentences can be highlighted, although this feature is usually seen only in children’s books. Finally, the least common of the audio additions is background music, but this feature is rare and is supported only through Apple’s iBookstore.

Video

This is the most common addition to enhanced e-books but also one of the most restrictive. Full-length videos can be embedded in the file without need for an internet connection, but many e-book retailers have file size limits that can limit length or quality. Like audio files, videos are best included after relevant passages in the text. With these restrictions in mind, IU Press recommends that you use only short relevant videos as a supplement to the text rather than as a substitution for it. Each video should also include a poster image, or thumbnail, to display before the video is played, and at least one black frame at the beginning and end.

Animation

Another enhancement is simple animation. These animations are created in layers with CSS (Cascading Style Sheets) and are only two-dimensional. Animations are most commonly used in children’s books but are technically possible in other applications. This webpage has more information, as well as an example of what an e-book animation can look like: http://ebookarchitects.com/learn-about-ebooks/enhanced-ebooks/

Amazon

iBookstore

Kobo

Nook

Google Play

Max file size

650 MB

2 GB, 200 MB recommended

100 MB

20 MB

2 GB

Video

Supported on apps, not on Kindle Fire

Video contd.

H.264

H.264

—

H.264

—

Video contd.

MPEG-2

MPEG-4

—

—

—

Video contd.

MP4

.mv4 or .mp4

—

.3gp / .3g2 / .mp4

—

Video dimensions

Wide screen: 704x396 full screen: 640x480

640x480 or 640x 360 (SD), 1920x1080 (HD)

—

176x144 up to 854x480

—

Interlacing

Progressive

Progressive

—

—

—

Color space

4:2:0 YUV

ITU-R BT.709 (HD)

—

—

—

Video mode

VBR or CBR

VBR

—

—

—

Video bit rate

2500 kbps

40-60 mbps (SD) 220 mbps (HD)

—

—

—

Key frame interval

2 or 4 seconds

—

—

—

—

In-video audio

Encode

MP3

AAC

—

AAC LC / LTP or AAC HeV1 / HeV2

—

Mono/stereo

—

Stereo

—

—

—

Bit rate

256 kbps or higher

256 kbps

—

Up to 320 kbps

—

Sample rate

48 kHz recommended

All files must have same sample rate

—

—

—

Additional video specs

Must include caption, video time, poster image and black end frame.

Poster image 150 px by 300 px. End with one black frame.

—

—

—

Audio

Extension

.mp3

.m4a

—

Mp4, mp3, ogg, AAC

—

Encoding

MP3

AAC/MP4

—

MP4 ACC compressed only

—

Mono/stereo

Stereo

Stereo

—

Mono/stereo

—

Bit rate

128 to 256 kbps

256 kbps

—

Max 320 kbps

—

More information on enhanced e-books

These pages have more information on technical specs for enhancements as well as general information on these types of publications: